I have a very frustrating problem with my 95 3.4L.

When the engine is warm and under a load accelerating, it will back fire and chug and spit until it "catches its second wind". It wont stall out.

I have changed the MAP sensor, the EGR, I have 35-45psi of fuel presure constant and I have monitored it while driving and it is good.

I'm now leaning towards the ignition system. Since it happens under load and when hot, could it be ignition coils? It has new wires and plugs.

Furthur it smells rich, however the cat is gutted (on another whim).

Any suggestions?

 

the misfire codes dont apply until 96+.

the smell of raw gas is because you are misfiring and the gas is not getting burned.

i would investigate the plugs, then wires, then coils.

 

Thanks for your reply.

I have brand new coils and ignition module on the car now as well. The problem persists

I'm going to look at the plugs and wires real closely now, but I just put brand new ones in.

I'm really stumped on this one.

Can a throttle position sensor act up intermittantly without throwing a code?

 

I had the same problem in my 2000 v6 and i didn't get any codes. I found out that one of the coil pack electrodes was corroded. Good luck

 

I have ruled out the coils because there is now new coils and ignition module in it. I'm now leaning towards the fuel system...the fuel pressure is good, but I'll have to test the volume. Anyone know how many gallons per minute it is supposed to put out?

 

have you read the misfire stickie?

 

Ok this is starting to get annoying...

Still have the problem....getting worse...only happens when the engine is warm. Bucking and hesitation, intermittant backfire, under load.


So far, new plugs, wires, coils, ICM, EGR, TPS, IAT, Air Filter, Fuel Filter.

Fuel pressure is 43-45 when not running and key on, 35 psi running which is to specs. I've driven it and watched the fuel pressure and it doesnt dip or anything.

However last night I noticed that I had 22 degrees of advance at idle. This is way off. It should be 12-13 degrees at idle.

What would cause this? Cam position sensor? Crank position sensor? Remember no codes and very intermittant problem when engine warm (hardest to solve ) Let me know what you think and also the location of the sensor. I dont know where to find the Crank position sensor and the cam position sensor. Is the crank sensor at the flywheel or the harmonic balancer?

Thanks for your help

 

I'd say harmonic balancer
maybe clogged injectors or bad PCM? i dunno

 

Thanks Jonathon for your suggestions.

I'm going to get a used fuel rail with injectors and swap...that way i will know if the problem is better to just get new injectors.

I just found at the vehicle has a built in radical advance program which is really a coeffecient so when it says on a scanner that its 20-30 degrees advance, its really 12ish.

 

also try a higher octane gas and see if that might help

 

could be a number of things you arent thinking of:

(wont list ones you've already tried)
Crank sensor is bad (either the 24x (side) or 36x (front)), Cam sensor is bad, Fuel injectors are clogged, Fuel Injectors are bad, Fuel filter is clogged, bad gas (altho unlikely), or my personal favorite:

You have crank walk (this actually happened to me and exhibited the same issues you are describing)

 

Crank Walk, What Is This?? Could You Explain?

 

hows the map sensor readings/LT trims?

 

wow am i embarassed to write this...

It started missing terribly on one cylinder today. All the time. So I pulled over and on a whim (desperate last attempt ) checked all the spark plug wires. They were all fine but one felt a little weird.

I pulled it completely out and inspected it. I then put it back on and got the satisfying "click". But something wasn't quite right with it, so I pulled it out again, and tried again.

It was then I realized that the click was coming from the boot clicking into the spark plug metal protector and not the spark plug. This particular boot was manufactured 3/8" shorter than the rest of the boots and the metal protector prevented it from completely clicking onto the spark plug.

What bad luck eh? So i bought one new spark plug wire and it fit perfectly. Talk about a minor manufacturing error costing $$$!!

Thanks for all your help!

 

It's when the crank moves forward or rearward depending on the torque applied in the main bearing. Usually due to excessive clearances between the rods and crank journals.